<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <button>按钮1</button>
    <button>按钮2</button>
    <button>按钮3</button>
    <button>按钮4</button>
    <button>按钮5</button>
    <script>
        let btn = document.querySelectorAll('button');
        //btn得到的是伪数组每个元素的btn[i]
        for(var i = 0; i < btn.length; i++){
            btn[i].onclick=function(){
                for(var i= 0;i<btn.length;i++){
                    btn[i].style.backgroundColor = '';
                }
                this.style.backgroundColor = 'pink';
                
            }
        }
    </script>
</body>
</html>